Known in the art is U.S. Pat. No. 7,639,460 B2. This document describes a switching apparatus and a method for varying the impedance of a phase line of a segment of an electrical power line. The phase line includes n conductors electrically insulated from each other and short-circuited together at two ends of the segment. More particularly, the apparatus includes at least one first vacuum interrupter connected in series with at least one of the conductors, at least one first controllable motor for selectively opening and closing the at least one first vacuum interrupter, and a controller for controlling the at least one first controllable motor according to a parameter representative of the current operating conditions of the phase line. U.S. Pat. No. 7,639,460 B2 is herein incorporated by reference.
Also known is a paper by the inventor published in the January 2011 edition of the journal “Cold Regions Science and Technology” (volume 65, issue 1) entitled “Smart Power Line and photonic de-icer concepts for transmission-line capacity and reliability improvement”. The paper relates to a Smart Power Line concept, and its implementation on new or existing transmission lines. The Smart Power Line addresses three needs: line de-icing, line impedance modulation, and line monitoring.
Also known in the art is the U.S. Pat. No. 6,396,172 and the PCT application published under the international publication no. WO 02/41459. In these documents, there is described a switching apparatus also intended to be used with a segment of an electrical power line having several phase lines.
Also known in the art is U.S. Pat. No. 2,797,344. This patent describes an apparatus for deicing electric cables. This patent proposes that, in a power transmission line, a cable having a pair of conductors insulated from each other is provided. An electrical bridge is connected in series with one of the conductors. A means is provided for opening the electrical bridge, and another means is provided for operating the electrical bridge in response to ice accumulation on the cable. The electric bridge comprises a normally closed switch which is open by the means that responds to an ice accumulation on the cable.
Also known in the art is U.S. Pat. No. 4,082,962. This patent describes a device for melting the ice by direct current through conductors of an overhead power transmission line. This patent proposes the use of a rectifier that is temporarily connected to the end of one of the conductors of the line. The apparatus also comprises a grounding circuit as well as a circuit filter connected parallel to the rectifier. The circuit proposed in this patent uses a rectified current for deicing the line. For each section of the line, a rectifier, a grounding circuit and a circuit filter are used.
Also known in the art is U.S. Pat. No. 4,126,792. This patent proposes a high-voltage network for areas of increased intensity of icing. This patent proposes the use of a rectifier and a switching circuit for connecting at least one conductor of the line to the rectifier so as to melt the ice by a rectified current.
One of the drawbacks which can be found in at least some of the above-mentioned switching apparatuses and methods is that some of these apparatuses and methods may not allow for an efficient and safe switching of the conductors of a segment of an electric power line.
One of the objects of the present invention is to propose a switching apparatus and method for a segment of an electric power line which enables the interrupters of the conductors of a segment of the line to be switched between a closed and an open position, in an efficient, safe, and economical manner.
The objects, advantages and other features of the present invention will be more apparent upon the reading of the following non restrictive description of different optional embodiments given as examples only in reference with the attached drawings.